There are numerous machines which include a system for issuing tickets having specific items printed thereon. By way of example, mention may be made of cash registers which deliver receipt tickets. Conventional cash registers are operated by a check-out clerk, and the clerk can therefore refill the machine with paper on which to issue tickets whenever it runs out.
Some ticket-issuing machines operate without anybody being in permanent attendance. They therefore receive periodic maintenance only. This is typically true of machines which issue tickets in receipt of payment for parking. Such machines are described, for example, in the present Assignee's patent application No. 870,554. When such ticket dispensers are in use, a driver who wishes to leave a vehicle parked pays money into the dispenser corresponding to the desired parking time. In exchange for this sum of money, the dispenser issues the driver with a ticket that bears at least the current date and the time at which authorized parking will expire, given the amount paid. The driver then places the ticket behind the windscreen of the parked vehicle so that parking inspectors can verify whether the appropriate parking fee has been paid in respect of any parked vehicle.
If the ticket dispensing machine runs out of paper, then the machine needs putting "out of service" and this can cause a loss of revenue to the organization selling parking.
For such machines, maintenance essentially comprises periodically collecting the money paid thereto. It is thus very important for the person responsible for collecting this money to be informed when the strip of paper is nearly used up so that a new roll can be inserted.
Further, it must also be understood that when the paper is suitable for thermal printing and is also pre-printed, it is fairly expensive. It is thus particularly advantageous for the organization selling parking to put off replacing the rolls of paper to as late a moment as possible. However, the time at which the paper needs replacing depends both on the frequency with which maintenance personnel check the need to replace the paper and also on the frequency with which users cause the machine to issue tickets.
One proposal for solving this problem consists in mounting mechanical feeler systems in parking ticket dispensers in order to detect the thickness of the strip of paper remaining on the paper storage reel. The feeler keeps permanently in touch with the thickness of the reel and delivers an alarm signal when this thickness drops below a predetermined value. However, such a feeler is not very accurate in operation. Further it is difficult to adjust to give an alarm when the thickness of the paper remaining corresponds to the frequency with which the particular ticket-dispensing machine is used.
An aim of the present invention is to provide a ticket-issuing system having means for detecting when the supply of paper is running out in a manner which is reliable, which is easy to adjust, and which is readily adapted to a desired alarm threshold.